The present invention relates generally to switch gear and, more particularly, to a technique for obtaining current signals through power-conveying conductors routed to or from switch gear in a modular fashion.
A host of applications exist for switch gear for delivering electric power between a source and a load. In general, such switch gear includes contactors and relays of various types. The switch gear is generally placed in series with various other components, typically downstream of circuit protective components, such as fuses and circuit breakers, and upstream of components that apply the controlled power to a load. Such switch gear is used throughout industry, and in all commercial, mining, marine, and even consumer settings. In many applications, the switch gear is used to provide power for electric motors, although such loads are certainly not the only application of such switch gear.
Certain applications do or could benefit from enhanced control and monitoring functions if additional parameters were available for control circuitry, particularly parameters of electric power channeled through switch gear. For example, certain protective circuitry, such as fuses and thermal overload circuits, simply react to heating that results from high or excessive currents through the devices and conductors. For other types of control, however, an analog or digital current signal would be useful for analyzing system performance, detecting certain types of faults, predicting certain types of faults, and so forth. Where such signals have been needed, however, current sensors have typically been provided in an integrated fashion within the devices themselves. For example, relays are currently available that include integrated current sensors and logic devices that can act upon signals from the current sensors for control and monitoring. However, such integration of current sensors can add significantly to a cost of the base units, and reduces the flexibility of offering to the user devices with and without current sensing capabilities.
There is a need, in the art, for a different approach to acquisition of current signals. In particular, there is a need for a technique that can be added in a modular fashion to a contactor so as to acquire current signals when desired, but which may be eliminated if not needed. There is a also a need for a current sensing module for contactors that can be applied to either the line or the load side of a contactor, and that provides the possibility for integration with other input/output (I/O) elements and networks.